During Isaac H. Weldon's early childhood, his Irish immigrant parents moved with their large family to a farm south of Woodstock, Ont., where he attended high school. He moved to Toronto, apparently to study medicine, but went to work instead with his eldest brother, Thomas Andrew, manager of the office there of the E. B. Eddy Company, a leading maker of fine paper [see Ezra Butler Eddy*]. Isaac left the company in 1899 to join Laurentide Paper, a newsprint producer in Grand-Mère, Que., as its North American sales agent; four years later he became sales manager for Burgess Sulphite of New England, which manufactured chemical wood pulp.

In 1909 Weldon teamed up with a handful of American pulp and paper industrialists who, led by his long-time friend Smith Frederick Duncan, owned Bryant Paper of Kalamazoo, Mich. This clique formed the St Lawrence Paper Mills Company in Toronto to take over the fine-paper mill of the bankrupt Cornwall Paper Company at Mille Roches (Long Sault), Ont. Weldon was appointed president, and he and his wife took up residence in Toronto. In 1910 the group, which now included Thomas Weldon, purchased Montrose Paper in Thorold and Barber Paper and Coating Mills in Georgetown [see John Roaf Barber*]. The following year Isaac Weldon was a driving force behind the establishment of Interlake Tissue Mills at Merritton (St Catharines), which he would serve as vice-president until his death. Then, in 1913, the group incorporated Provincial Paper Mills under Weldon's presidency to consolidate the operations of St Lawrence, Montrose, and Barber. Weldon would build Provincial into one of Canada's largest producers of book, writing, and coated papers and would carve out a niche for it within the industry.

Although his business affairs were definitely his life's focus – he was a member of the Toronto Board of Trade and the Canadian Manufacturers' Association – he displayed the benevolent streak that also marked many of his contemporaries. A director of the Hospital for Sick Children, he supported the Toronto Playgrounds Association, the Art Gallery of Toronto, and the Boys' Industrial Home in Bowmanville. In his leisure he frequented the National, Granite, Lakeview Golf, and Royal Canadian Yacht clubs, and he maintained a valuable rural property, Summit Farm, north of Richmond Hill. According to one biographer, he was "a man of simple tastes, a delightful and many-sided companion" who possessed a "keen sense of humour" and "showed easy tolerance of the mistakes of others."

Weldon personified his era's progressive business ethos: his strength lay not in technical expertise but in industrial entrepreneurialism. Whereas newsprint, which most of the country's mills manufactured, was sold duty-free in the United States, the fine papers made by Weldon's companies (mainly for books and magazines) were subjected to prohibitive tariffs. This situation forced him to concentrate on the relatively small domestic market, where one of Provincial's clients, Eaton's, needed large supplies of paper for its famous catalogues. To meet the market challenge, Weldon both expanded his product lines and fostered cooperation among producers. He was a co-founder of the Canadian Pulp and Paper Association in 1913, its first vice-president the following year, and president in 1915. In 1918 he took Provincial in as an inaugural member of the Canadian Paper Trade Association, which represented Canada's few fine-paper makers and many of its paper-goods producers, among them W. J. Gage and Company [see Sir William James Gage]. To maximize members' profits and create barriers against potential rivals, it divided the country into sales zones, developed guidelines for standardizing products, and enforced a common sales policy. The upshot was a steady rise in consumption, few new players, and consistent profits.

Vertical integration was another step that Weldon took to consolidate his position. Provincial Paper controlled three converting mills, which turned pulp into paper, but it still purchased its pulp on the open market. To remedy this situation, over the course of 1916–17 Port Arthur Pulp and Paper was incorporated as a subsidiary with Weldon as president and a mill was erected in Port Arthur (Thunder Bay), Ont., to turn spruce into the sulphite pulp required by Provincial's other plants. In 1920 he and his partners incorporated a new Provincial Paper Mills company, of which Weldon continued as president, to combine formally the securities and assets of Provincial and Port Arthur Pulp and Paper.

Isaac Weldon was renowned for his managerial skills, which he amply demonstrated in his dealings with the Ontario government. Prior to constructing the Port Arthur mill, in 1917 Provincial had applied for a pulpwood limit to support the plant, but it lost in the bidding for the tract. Thwarted in his subsequent efforts to secure a long-term timber supply – the sine qua non for a pulp and paper mill – Weldon tried a different tack in 1920, with the new United Farmers government of Ernest Charles Drury*. Provincial reapplied for another large limit, but this time he exerted pressure by threatening to cut off the supply of paper to magazine publishers if the government did not deliver the tract he wanted. Led by Harold Theodore Gagnier of Saturday Night (Toronto), the publishers lobbied Drury to grant Provincial's wish. Provincial concomitantly made a special offer. The Department of Education had traditionally experienced difficulty in purchasing the quantity of paper it needed for textbooks at prices it considered reasonable. Provincial proposed to supply the paper in exchange for the limit. An agreement was signed in July 1921 and thereafter Provincial enjoyed a relationship with the government that ensured it had more than enough timber.

Weldon's association with Provincial ended in 1927, when Dominion Securities of Toronto gained control by purchasing its common stock. By this time he had established himself as one of the pioneers in Canada's modern pulp and paper industry. He died in Toronto in 1928 and was buried in Mount Pleasant Cemetery.

We acknowledge the support of the Government of Canada through the Department of Canadian Heritage. Nous reconnaissons l’appui du gouvernement du Canada par l’entremise du ministère du Patrimoine canadien.